Pmc21 C2v2 mm2 Orthorhombic info
No. 26 Pmc21 Patterson symmetry Pmmm

symmetry group diagram

Origin on m c 21

Asymmetric unit 0 ≤ x ≤ 1/2; 0 ≤ y ≤ 1/2; 0 ≤ z ≤ 1

Symmetry operations

(1)  1   (2)  2(0, 0, 1/2)   0, 0, z(3)  c   x, 0, z(4)  m   0, y, z

Generators selected (1); t(1, 0, 0); t(0, 1, 0); t(0, 0, 1); (2); (3)

Positions

Multiplicity, Wyckoff letter,
Site symmetry		 Coordinates Reflection conditions
 General:
4 c 1
(1) x, y, z(2) -x, -y, z + 1/2(3) x, -y, z + 1/2(4) -x, y, z
h0l : l = 2n
00l : l = 2n
    Special: as above, plus
2 b  m . . 
1/2, y, z 1/2, -y, z + 1/2
no extra conditions
2 a  m . . 
0, y, z 0, -y, z + 1/2
no extra conditions

Symmetry of special projections

Along [001]   p2mm
a' = a   b' = b   
Origin at 0, 0, z		Along [100]   p1g1
a' = b   b' = c   
Origin at x, 0, 0		Along [010]   p11m
a' = 1/2c   b' = a   
Origin at 0, y, 0

Maximal non-isomorphic subgroups

I [2] P1c1 (Pc, 7)1; 3
  [2] Pm11 (Pm, 6)1; 4
  [2] P1121 (P21, 4)1; 2
IIa none
IIb[2] Pmn21 (a' = 2a) (31); [2] Pbc21 (b' = 2b) (Pca21, 29); [2] Cmc21 (a' = 2a, b' = 2b) (36)

Maximal isomorphic subgroups of lowest index

IIc[2] Pmc21 (a' = 2a) (26); [2] Pmc21 (b' = 2b) (26); [3] Pmc21 (c' = 3c) (26)

Minimal non-isomorphic supergroups

I[2] Pmma (51); [2] Pbam (55); [2] Pbcm (57); [2] Pnma (62)
II[2] Cmc21 (36); [2] Amm2 (38); [2] Bme2 (Aem2, 39); [2] Ima2 (46); [2] Pmm2 (c' = 1/2c) (25)








































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